1. Field of the Invention
The present invention relates to a magnetic recording apparatus using a magnetoresistance reproducing head.
2. Description of the Related Art
An MR head using magnetoresistance (MagnetoResistance; hereinafter referred to as MR) is expected as one which can be used for a high density magnetic recording apparatus. The MR head has such a structure that upper and lower magnetic shielding films are disposed above and below a magnetoresistance element through magnetic gap films, respectively. The MR head is stacked with an induction type recording head using the upper magnetic shielding film as its lower recording magnetic pole, and this stacked head is known as a recording/reproduction composite magnetic head.
FIG. 15 is a side view of a medium facing surface: ABS (Air Baring Surface), which shows the structure of a conventional recording/reproduction composite magnetic head. As shown in FIG. 15, an MR film 4 is formed through a lower magnetic gap film 3 of an alumina film or the like on a lower magnetic shielding film 2 of CoZrNb amorphous alloy, or the like, formed on a substrate 1 of altic (A1.sub.2 O.sub.3 . TiC) with alumina.
The MR film 4 is patterned in stripe shape, and as shown in FIG. 15, a pair of lead electrodes 5 are connected to both ends thereof. The lead electrodes 5 are made of good conductive films with a thickness of about 100 nm. As shown in FIG. 15, an upper magnetic shielding film 8 is formed through an upper magnetic gap film 7 on an MR element 6 including the MR film 4 and the lead electrodes 5. A reproducing MR head 9 is constituted by the MR element 6, the upper and lower gap films 3 and 7, and the upper and lower magnetic shielding films 2 and 8.
An induction type recording head 10 includes, as shown in FIG. 15, a recording magnetic pole serving also as the upper magnetic shielding film 8, a recording magnetic gap film 11 made of an alumina film or the like, and an upper recording magnetic pole 12, and further includes a recording coil (not shown) for applying a recording magnetic field to the recording magnetic poles 8 and 12 at the rear of the ABS.
The increase of recording density of a magnetic recording apparatus, such as a HDD, has been achieved by narrowing a track, narrowing a gap, shortening a bit length of a recording signal, or the like. For example, for the purpose of achieving the high recording density such as 4 Gbpsi (Giga-bits/inch.sup.2), in addition to shortening of a track width, it is necessary to shorten a bit length by making a reproducing gap length between the upper and lower magnetic shielding films 2 and 8 (distance from the film thickness center of the magnetic field detecting film to the upper and lower magnetic shielding films) to have a length of about 160 nm. For the purpose of achieving such a narrow gap, it is necessary to provide stable insulation coating on the lead electrodes 5 having a thickness of about 100 nm while using the thin upper magnetic gap film 7 having a thickness of about 60 nm at one side.
In the present film forming technique, it is difficult to achieve high recording density such as 10 Gbpsi or more and to secure excellent insulation between the lead electrodes 5 and the upper magnetic shielding film 8.
In addition, the width of an isolated reproduction signal as an index of a reproduction resolution is 280 nm even in the present level of about 4 Gbpsi, and its fluctuation is about 70 nm. For such a width of an isolated reproduction wave output, a desirable gap length becomes almost zero.
On the other hand, Japanese Patent Unexamined Publication No. Hei. 9-138918 discloses an MR head in which an operation point is adjusted by making upper and lower gap lengths different from each other.
As described above, in a conventional magnetic recording apparatus, it becomes difficult to realize a gap length meeting a high recording density system such as 10 Gbpsi or more.